Risk factors for perineal injury during delivery

OBJECTIVE: We sought to identify risk factors for anal sphincter injury during vaginal delivery. STUDY DESIGN: This was a retrospective, case-control study. We reviewed 2078 records of vaginal deliveries within a 2-year period from May 1, 1999, through April 30, 2001. Cases (n = 91) during the study period were defined as parturients who had documentation of greater than a second-degree perineal injury. Control subjects (n = 176), who were identified with the use of a blinded protocol, included women who were delivered vaginally with less than or equal to a second-degree perineal injury. For each patient, we reviewed medical and obstetrics records for the following characteristics: maternal age, race, weight, gestational age, parity, tobacco use, duration of first and second stages of labor, use of oxytocin, use of forceps or vacuum, infant birth weight, epidural use, and episiotomy use. RESULTS: Of the 2078 deliveries that were reviewed, we discovered 91 cases (4.4%) of documented anal sphincter injury. The mean maternal age of our sample was 24.9 +/- 5.9 years). Nearly two thirds (63.2%) were white; 26.7% were black, and 10.1% were of other racial backgrounds. Forceps were used in 51.6% of deliveries that resulted in tears (cases), compared to 8.6% of deliveries without significant tears (control subjects, P <.05). Using cases and control subjects with complete data (cases, 82; control subjects, 144), delivery with forceps was associated with a 10-fold increased risk of perineal injury (odds ratio, 10.8; 95% CI, 5.2-22.3) compared to noninstrumented deliveries. The association was similar after adjustment for age, race, parity, mode of delivery, tobacco use, episiotomy, duration of labor (stages 1 and 2), infant birth weight, epidural, and oxytocin use (odds ratio, 11.9; 95% CI, 4.7-30.4). Nulliparous women were at increased risk for tears (adjusted odds ratio, 10.0; 95% CI, 3.0-33.3) compared with multiparous patients, but parity did not reduce the association between forceps-assisted deliveries and anal sphincter injuries. Increasing fetal weight was also a risk factor in both unadjusted and adjusted analyses. The performance of a midline episiotomy was associated with an increased risk of anal sphincter tear compared with delivery without an episiotomy in the univariate analysis (odds ratio, 4.9; 95% CI, 2.5-9.6), but this association was reduced in the adjusted analysis (odds ratio, 2.5; 95% CI, 1.0-6.0). The increased duration of both the first and second stages of labor increased injury risk in the unadjusted, but not adjusted, analysis. No significant association was observed between case status and the use of oxytocin or epidural anesthesia. Greater, but not significant, increased risk was associated with maternal indications for operative delivery compared with fetal indications. CONCLUSION: Our results are consistent with recent reports that identify forceps delivery and nulliparity as risk factors for recognized anal sphincter injury at the time of vaginal delivery. Further investigation should focus on the determination of whether the association of injury to instrumentation is causal or, in fact, modifiable. Because of the established association between sphincteric muscular damage and anal incontinence, patients should be counseled about the risk of anal sphincter injury when operative vaginal delivery is contemplated. Such patients should be followed closely in the postpartum setting to assess for the development of potential anorectal complaints.     

Trends in major modifiable risk factors for severe perineal trauma, 1996–2006

OBJECTIVE: To examine what effect the major modifiable risk factors for severe perineal trauma have had on the rates of this trauma over time. METHODS: A retrospective observational cohort study of singleton vaginal deliveries taken from a perinatal database for the period 1996 through 2006. RESULTS: A total of 46,239 singleton vertex vaginal deliveries met the inclusion criteria. Major risk factors for severe perineal trauma were increased maternal age (odds ratio [OR] 1.28, 95% confidence interval [CI] 1.1-1.5), non-African American ethnicity (OR 1.5, 95% CI 1.3-1.7), nulliparity (OR 4.8, 95% CI 4.11-5.6), fetal birth weight (OR 2.2, 95% CI 1.9-2.4), forceps (OR 8.3, 95% CI 5.4-10.8), vacuum (OR 2.9, 95% CI 1.9-4.4), and midline episiotomy (OR 5.7, 95% CI 5.0-6.4). Evaluation of the changes in rates of these factors over the study period revealed that the decline in the rates of episiotomy and the use of forceps accounted for a reduction in severe lacerations of more than 50%. CONCLUSION: Reduction of severe perineal trauma by restricted use of the 2 modifiable clinical variables, episiotomy and forceps, is evident over time.     

Impact of Episiotomy During Operative Vaginal Delivery on Obstetrical Anal Sphincter Injuries

ObjectiveThe purpose of this study was to describe associations between episiotomy at the time of forceps or vacuum-assisted delivery and obstetrical anal sphincter injuries (OASIS).MethodsThis population-based retrospective cohort study used delivery information from a provincial perinatal clinical database. Full-term, singleton, in-hospital, operative vaginal deliveries of vertex-presenting infants from April 1, 2006 to March 31, 2016 were identified. Odds ratios (ORs) and 95% confidence intervals (CIs) for associations between episiotomy and third- or fourth-degree lacerations were calculated in multiple logistic regression models (Canadian Task Force Classification II-2).ResultsEpisiotomy was performed in 34% of 52 241 operative vaginal deliveries. OASIS occurred in 21% of forceps deliveries and 7.6% of vacuum deliveries. Episiotomy was associated with increased odds of severe perineal lacerations for vacuum deliveries among women with (OR 2.48; 95% CI 1.96–3.13) and without (OR 1.12; 95% CI 1.02–1.22) a prior vaginal delivery. Among forceps deliveries, episiotomy was associated with increased odds of OASIS for those with a previous vaginal delivery (OR 1.52; 95% CI 1.12–2.06), but it was protective for women with no previous vaginal delivery (OR 0.73; 95% CI 0.67–0.79). Midline compared with mediolateral episiotomy increased the odds of OASIS in forceps deliveries (OR 2.73; 95% CI 2.37–3.13) and vacuum deliveries (OR 1.94; 95% CI 1.65–2.28).ConclusionIn conclusion, results suggest that episiotomy should be used with caution, particularly among women with a previous vaginal delivery and in the setting of vacuum-assisted delivery. Episiotomy may protect against OASIS in forceps-assisted deliveries for women without a prior vaginal delivery.     

Decreased anal sphincter lacerations associated with restrictive episiotomy use

OBJECTIVE: To determine whether restrictive episiotomy use was associated with decreases in anal sphincter lacerations and the risk of anal sphincter laceration attributable to episiotomy. STUDY DESIGN: This was a retrospective database study. Rates of episiotomy, anal sphincter laceration (third- or fourth-degree tear), and other confounding variables were compared among vaginal deliveries before (1999) and after (2002) restrictive episiotomy use was implemented at our institution. Logistic regression was used to estimate the odds ratio of anal sphincter laceration that was due to episiotomy and other variables. RESULTS: The episiotomy rate decreased 56% (37% to 17%, P < .001) between 1999 and 2002, whereas the anal sphincter laceration rate decreased 44% (9.7% to 5.4%, P < .001). There were no changes in age, race, nulliparity, prolonged second stage of labor, operative vaginal deliveries, birth weight, or macrosomia, although oxytocin use and epidural use decreased slightly (37% to 31%, P < .001, and 80% to 76%, P = .02, respectively). The adjusted odds ratio of anal sphincter laceration attributable to episiotomy decreased 55%, from 6.5 (95% CI: 3.8, 11.1) to 2.9 (95% CI: 1.7, 5.0), between 1999 and 2002. Conversely, the adjusted odds ratios of anal sphincter laceration attributable to the other independent risk factors all increased or remained the same: operative vaginal delivery, which increased from 4.4 (95% CI: 2.7, 6.9) to 6.3 (95% CI: 3.6 11.1); nulliparity, from 2.9 (95% CI: 1.8, 4.8) to 2.9 (95% CI: 1.4, 5.9); macrosomia, from 1.9 (95% CI: 1.1, 3.4) to 2.6 (95% CI: 1.3, 5.4); and prolonged second stage, from 2.0 (95% CI: 1.3, 3.0) to 2.1 (95% CI: 1.2, 3.7). CONCLUSION: With restrictive episiotomy use, the episiotomy rate, anal sphincter laceration rate, and risk of anal sphincter laceration attributable to episiotomy were all reduced by approximately 50%.     

Mediolateral episiotomy reduces the risk for anal sphincter injury during operative vaginal delivery

Objective  To determine the risk factors for anal sphincter injuries during operative vaginal delivery.
Setting and design  A population-based observational study.
Population  All 21 254 women delivered with vacuum extraction and 7478 women delivered with forceps, derived from the previously validated Dutch National Obstetric Database from the years 1994 to 1995.
Methods  Anal sphincter injury was defined as any injury, partial or complete, of the anal sphincters. Risk factors were determined with multivariate logistic regression analysis.
Main outcome measures  Individual obstetric factors, e.g. fetal birthweights, duration of second stage, etc.
Results  Anal sphincter injury occurred in 3.0% of vacuum extractions and in 4.7% of forceps deliveries. Primiparity, occipitoposterior position and fetal birthweight were associated with an increased risk for anal sphincter injury in both types of operative vaginal delivery, whereas duration of second stage was associated with an increased risk only in vacuum extractions. Mediolateral episiotomy protected significantly for anal sphincter damage in both vacuum extraction (OR 0.11, 95% CI 0.09–0.13) and forceps delivery (OR 0.08, 95% CI 0.07–0.11). The number of mediolateral episiotomies needed to prevent one sphincter injury in vacuum extractions was 12, whereas 5 mediolateral episiotomies could prevent one sphincter injury in forceps deliveries.
Conclusions  Primiparity and occipitoposterior presentation are strong risk factors for the occurrence of anal sphincter injury during operative vaginal delivery. The highly significant protective effect of mediolateral episiotomies in both types of operative vaginal delivery warrants the conclusions that this type of episiotomy should be used routinely during these interventions to protect the anal sphincters.     

Risk factors for severe perineal tear: can we do better?

Our aim was to investigate the risk factors associated with severe perineal tears defined as either third- or forth-degree tears and, ultimately, find strategies for prevention. We carried a retrospective analysis of a computerized perinatal database, collected prospectively, from a single county hospital between January 1, 1993 and June 30, 1998. Singleton vaginal vertex deliveries were analyzed for potential risk factors using univariate and multiple logistic regression analysis including all two-way interactions. Severe perineal tear occurred in 1905 (8.2%) of 23,244 vaginal deliveries. In the multiple logistic regression analysis, the following factors carried a significantly higher risk for severe laceration: midline episiotomy, primary vaginal delivery, use of pudendal block, forceps deliveries, and birth weight more than 4000 g. The study of interactions demonstrated that mediolateral episiotomy was associated with an increased risk for severe tear only during the first vaginal delivery, but not during a repeat vaginal delivery. Our data suggest that primary vaginal delivery, fetal weight above 4000 g, and the use of pudendal analgesia can help identify in advance patients at highest risk for severe perineal tear. During the delivery of these patients usage of vacuum (instead of forceps) and restricting the use of midline episiotomy might reduce the incidence of severe perineal tear. In cases where episiotomy seems crucial, the use of a mediolateral episiotomy may reduce the likelihood of severe perineal tear.     

Cohort study of maternal and neonatal morbidity in relation to use of episiotomy at instrumental vaginal delivery

OBJECTIVE: The aim of this study was to investigate the maternal and neonatal morbidity related to use of episiotomy for vacuum and forceps deliveries. DESIGN: Retrospective population-based cohort study. SETTING: Dundee, Scotland. POPULATION: Two thousand one hundred and fifty three women who experienced an instrumental vaginal delivery between January 1998 and December 2002. METHODS: Univariate and multivariate logistic regression analyses were performed comparing deliveries with and without the use of episiotomy. MAIN OUTCOME MEASURES: Extensive perineal tears (third and fourth degree) and shoulder dystocia. RESULTS: Two hundred and forty-one (11%) of the 2153 women who underwent instrumental vaginal deliveries did not receive an episiotomy. Vacuum delivery was associated with less use of episiotomy compared with forceps (odds ratio 0.10, 95% CI 0.07-0.14). Extensive perineal tears were more likely with use of episiotomy (7.5%vs 2.5%, adjusted OR 2.92, 95% CI 1.27-6.72) as was neonatal trauma (6.0%vs 1.7%, adjusted OR 2.62, 95% CI 1.05-6.54). Use of episiotomy did not reduce the risk of shoulder dystocia (6.9%vs 4.6%, adjusted OR 1.43, 95% CI 0.74-2.76). The findings were similar for delivery by vacuum and forceps. CONCLUSION: The use of episiotomy increased the risk of extensive perineal tears without a reduction in the risk of shoulder dystocia.     

Third degree perineal tears in a university medical center where midline episiotomies are not performed

Objective Midline episiotomy is a known major risk factor for severe perineal lacerations. The study was aimed to define obstetric risk factors for third-degree perineal tears in a university medical center where midline episiotomies are not performed.Study design A comparison between vaginal deliveries complicated with third-degree perineal tears and deliveries without third-degree perineal tears was performed. Deliveries occurred between the years 1988–1999 in a tertiary medical center. Multiple gestations, preterm deliveries (<37 weeks gestation), cesarean deliveries and cases of shoulder dystocia were excluded from the analysis. A multiple logistic regression model was constructed in order to find independent risk factors for third-degree perineal tears. Odds ratios (OR) and their 95% confidence interval (CI) were calculated from the regression coefficient.Results During the study period, 79 (0.1%) consecutive cases of third degree perineal tears were identified. Significant risk factors from the univariate analysis were fetal macrosomia (OR 2.7, 95%CI 1.2–5.5), nulliparity (OR 2.9, 95%CI 1.8–4.6), labor induction (OR 1.9, 95%CI 1.0–3.5), failure of labor to progress during the second stage (OR 10.8, 95%CI 5.4–21.1), non-reassuring fetal heart rate patterns (OR 11.7, 95%CI 6.1–21.5), mediolateral episiotomy (OR 2.8, 95%CI 1.8–4.5), vacuum extraction (OR 10.6, 95%CI 6.1–18.3), and forceps delivery (OR 29.2, 95%CI 7.3–97.2). However, using a multivariable analysis, only fetal macrosomia (OR 2.5, 95%CI 1.2–4.9), vacuum extraction (OR 8.2, 95%CI 4.7–14.5), and forceps delivery (OR 26.7, 95%CI 8.0–88.5) remained as independent risk factors. The combined risk for instrumental deliveries of macrosomic newborns was 8.6 (95% CI 1.2–62.5; p=0.010).Conclusions After adjustment for possible confounding variables, mediolateral episiotomy per se was not an independent risk factor for third-degree perineal tears. Instrumental vaginal deliveries of macrosomic fetuses should be avoided whenever possible to decrease the occurrence of third-degree perineal tears.Presented in part at the Society for Gynecologic Investigation 50th Annual Scientific Meeting, Washington, DC, 27–30 March 2003     

Risk factors for anal sphincter tear during vaginal delivery

OBJECTIVE: To identify risk factors associated with anal sphincter tear during vaginal delivery and to identify opportunities for preventing this cause of fecal incontinence in young women. METHODS: We used baseline data from two groups of women who participated in the Childbirth and Pelvic Symptoms (CAPS) study: those women who delivered vaginally, either those with or those without a recognized anal sphincter tear. Univariable analyses of demographic and obstetric information identified factors associated with anal sphincter tear. We calculated odds ratios (ORs) for these factors alone and in combination, adjusted for maternal age, race, and gestational age. RESULTS: We included data from 797 primaparous women: 407 with a recognized anal sphincter tear and 390 without. Based on univariable analysis, a woman with a sphincter tear was more likely to be older, to be white, to have longer gestation or prolonged second stage of labor, to have a larger infant (birth weight/head circumference), or an infant who was in occiput posterior position, or to have an episiotomy or operative delivery. Logistic regression found forceps delivery (OR 13.6, 95% confidence interval [CI] 7.9-23.2) and episiotomy (OR 5.3, 95% CI 3.8-7.6) were strongly associated with a sphincter tear. The combination of forceps and episiotomy was markedly associated with sphincter tear (OR 25.3, 95% CI 10.2-62.6). The addition of epidural anesthesia to forceps and episiotomy increased the OR to 41.0 (95% CI 13.5-124.4). CONCLUSION: Our results highlight the existence of modifiable obstetric interventions that increase the risk of anal sphincter tear during vaginal delivery. Our results may be used by clinicians and women to help inform their decisions regarding obstetric interventions. LEVEL OF EVIDENCE: II.     

Risk factors for third degree perineal ruptures during delivery

Objective To determine risk factors for the occurrence of third degree perineal tears during vaginal delivery.
Design A population-based observational study.
Population All 284,783 vaginal deliveries in 1994 and 1995 recorded in the Dutch National Obstetric Database were included in the study.
Methods Third degree perineal rupture was defined as any rupture involving the anal sphincter muscles. Logistic regression analysis was used to assess risk factors.
Main outcome measures An overall rate of third degree perineal ruptures of 1.94% was found. High fetal birthweight, long duration of the second stage of delivery and primiparity were associated with an elevated risk of anal sphincter damage. Mediolateral episiotomy appeared to protect strongly against damage to the anal sphincter complex during delivery (OR: 0.21, 95% CI: 0.20–0.23). All types of assisted vaginal delivery were associated with third degree perineal ruptures, with forceps delivery (OR: 3.33, 95%-CI: 2.97–3.74) carrying the largest risk of all assisted vaginal deliveries. Use of forceps combined with other types of assisted vaginal delivery appeared to increase the risk even further.
Conclusions Mediolateral episiotomy protects strongly against the occurrence of third degree perineal ruptures and may thus serve as a primary method of prevention of faecal incontinence. Forceps delivery is a stronger risk factor for third degree perineal tears than vacuum extraction. If the obstetric situation permits use of either instrument, the vacuum extractor should be the instrument of choice with respect to the prevention of faecal incontinence.     

Immediate maternal and neonatal effects of forceps and vacuum-assisted deliveries

OBJECTIVE: To estimate the differences in immediate maternal and neonatal effects of forceps and vacuum-assisted deliveries. METHODS: We conducted a medical record review of all forceps and vacuum-assisted deliveries that occurred from January 1, 1998, to August 30, 1999, at Winthrop-University Hospital. Maternal demographics and delivery characteristics were recorded. Maternal outcomes, such as use of episiotomy and presence of lacerations, were studied. Neonatal outcomes evaluated were Apgar scores, neonatal intensive care unit admissions, cephalohematomas, instrument marks and bruising, and caput and molding. RESULTS: Of 508 operative vaginal deliveries, 200 were forceps and 308 were vacuum assisted. Forceps were used more often than vacuum for prolonged second stage of labor (P =.001). There was a higher rate of epidural (P =.02) and pudendal (P <.001) anesthesia, episiotomies (P =.01), maternal third- and fourth-degree perineal (P <.001) and vaginal lacerations (P =.004) with the use of forceps, whereas periurethral lacerations were more common in vacuum-assisted (P =.026) deliveries. More instrument marks and bruising (P <.001) were found in the neonates delivered by forceps, whereas there was a greater incidence of cephalohematomas (P =.03) and caput and molding (P <.001) in the neonates delivered with vacuum. Multivariable logistic regression analysis showed that forceps use was associated with an increase in major perineal and vaginal tears (odds ratio [OR] 1.85; 95% confidence interval [CI] 1.27, 2.69; P =.001), an increase in instrument marks and bruising (OR 4.63; 95% CI 2.90, 7.41; P <.001) and a decrease in cephalohematomas (OR 0.49; 95% CI 0.29, 0.83; P =.007) compared with the vacuum. CONCLUSIONS: Maternal injuries are more common with the use of forceps. Neonates delivered with forceps have more facial injuries, whereas neonates delivered with vacuum have more cephalohematomas. LEVEL OF EVIDENCE: II-3     

The role of mediolateral episiotomy during labour: analysis of risk factors for obstetric anal sphincter tears

BACKGROUND: To determine risk factors for third-degree and complete third- or fourth-degree anal sphincter tears in vaginal delivery. METHODS: This is a retrospective comparative study. Fifty-three women who had sustained an anal sphincter tear were compared with 9,178 women without such a complication between August 1997 and October 2001. Obstetric data was collected from an electronic database. The main outcome measures were odds ratios. RESULTS: In the whole study population, odds ratios (ORs) for third-degree tears were: primiparity, 8.34 (95% confidence interval [CI] 3.98-17.48); vacuum extraction, 5.22 (95% CI 2.69-10.13); parietal presentation, 3.97 (95% CI 1.16-13.64); and birth weight >4,000 g, 3.77 (95% CI 2.11-6.68); and for complete third- or fourth-degree tears odds ratios were 5.42, 2.98, 5.64, and 3.01, respectively. In multivariate analysis, mediolateral episiotomy appeared to be protective as regards third-degree tears (OR 0.37 [95% CI 0.2020-0.70]). CONCLUSIONS: Vacuum-assisted vaginal delivery bears an increased risk of third-degree anal sphincter tears in a maternity unit where forceps are not used. Restricted use of mediolateral episiotomy may have a protective effect on the perineum.     

Epidural analgesia and third- or fourth-degree lacerations in nulliparas.

OBJECTIVE: To determine if epidural analgesia is associated with differences in rates of severe perineal trauma during vaginal deliveries. METHODS: We studied 1942 consecutive, low-risk, term, vaginal deliveries in nulliparas, including spontaneous and induced labors, at a single institution from December 1994 to August 1995. The rate of third- and fourth-degree lacerations was compared for women who had and did not have epidural analgesia for labor-pain relief. Statistical significance was determined using chi2. Logistic regression analyses were used to evaluate associations while controlling for possible confounding variables. RESULTS: Overall rates of third- and fourth-degree lacerations were 10.8% (n = 210) and 3.4% (n = 63), respectively. Epidural analgesia was given to 1376 (70.9%) women. Among women who had epidurals, 16.1% (221 of 1376) had severe perineal lacerations compared with 9.7% (n = 55) of the 566 women who did not have epidurals (P < .001; odds ratio [OR] 1.8, 95% confidence interval [CI] 1.3, 2.4). When controlling for birth weight, use of oxytocin, and maternal age in logistic regression analysis, epidural remained a significant predictor of severe perineal injury (OR 1.4, 95% CI 1.0, 2.0). Epidural use is consistently associated with increased operative vaginal deliveries and consequent episiotomies, so we constructed a logistic regression model to evaluate whether the higher rates of those procedures were responsible for the effect of epidurals on severe perineal traumas. With operative vaginal delivery and episiotomy in the model, epidural was no longer an independent predictor of perineal injury (OR 0.9, 95% CI 0.6, 1.3). CONCLUSION: Epidural analgesia is associated with an increase in the rate of severe perineal trauma because of the more frequent use of operative vaginal delivery and episiotomy.     

Risk factors for third-degree perineal tears in vaginal delivery, with an analysis of episiotomy types

OBJECTIVE: To determine the risk factors for third-degree perineal tears during vaginal delivery and to investigate the relation between different types of episiotomy and the occurrence of such tears. STUDY DESIGN: This retrospective multicenter study consisted of an analysis of data from the delivery databases of the University Hospital of Vienna and Semmelweis Frauenklinic Wien between February and July 1999. The study was restricted to a sample that included all women with uncomplicated pregnancy as well as uncomplicated first and second stages of labor, gestational age > 37 weeks and a pregnancy with cephalic presentation. Women with multiple gestations, noncephalic presentation, cesarean deliveries, shoulder dystocia and gestational age < or = 37 weeks were excluded from the study. RESULTS: Among the 1,118 births, 37 women (3.3%) experienced third-degree perineal tears. The use of episiotomy per se and the type of episiotomy (midline) as well as forceps delivery, primiparity, large infant head diameter, prolonged second stage of labor and use of oxytocin were identified as risk factors for third-degree perineal tears during vaginal delivery. When analyzing different types of episiotomy, there was approximately a sixfold-higher risk of third-degree perineal tears in women undergoing midline episiotomy as compared to mediolateral episiotomy. A stepwise logistic regression analysis revealed that episiotomy, prolonged second stage of labor and large infant head diameter remained independent risk factors for third-degree perineal tears. CONCLUSION: We found several risk factors for third-degree perineal tears. The use of midline episiotomy was associated especially with an increased risk of severe anal sphincter tears. To prevent women from long-term sequelae due to third-degree perineal tears, avoidable risk factors should be minimized whenever possible.     

Risk factors for birth canal lacerations in primiparous women

Lacerations of the birth canal are common side effects of vaginal birth. They are potentially preventable. Although serious long-term consequences have been identified for severe perineal lacerations, less attention has been paid to lacerations in other locations and how the risk factors vary for different lacerations. We analyzed a dataset including 1009 primiparous women with singleton pregnancies and vaginal deliveries, and we examined risk factors for third- and fourth-degree perineal lacerations and periurethral, vaginal, and labial lacerations using logistic regression analysis. Large fetal size (> or = 3500 g) substantially increased the risk of perineal (odd ratio [OR], 3.8; 95% confidence interval [CI], 1.8 to 7.9) and periurethral (OR, 2.3; 95% CI, 1.0 to 5.0) lacerations but not other types of lacerations. Episiotomy had no impact on perineal lacerations (OR 0.9) but had very strong protective effects for other lacerations (OR 0.1). Prolonged second stage of labor (> 120 minutes) increased the risk of perineal and vaginal lacerations but reduced the risk for periurethral lacerations. Instrumental deliveries were significant risk factors for third- and fourth-degree perineal lacerations, with by far the strongest effect for low forceps (OR 25.0 versus < 3 for outlet forceps, outlet vacuum, and low vacuum). We concluded that separating different birth canal lacerations is critical in identifying risk factors and potential preventive strategies.     

The impact of occiput posterior fetal head position on the risk of anal sphincter injury in forceps-assisted vaginal deliveries

OBJECTIVE: A forceps-assisted vaginal delivery is a well-recognized risk factor for anal sphincter injury. Some studies have shown that occiput posterior (OP) fetal head position is also associated with an increased risk for third- or fourth-degree lacerations. The objective of this study was to assess whether OP position confers an incrementally increased risk for anal sphincter injury above that present with forceps deliveries. STUDY DESIGN: This was a retrospective cohort study of 588 singleton, cephalic, forceps-assisted vaginal deliveries performed at our institution between January 1996 and October 2003. Maternal demographics, labor and delivery characteristics, and neonatal factors were examined. Statistical analysis consisted of univariate statistics, Student t test, chi2, and logistic regression. RESULTS: The prevalence of occiput anterior (OA) and OP positions was 88.4% and 11.6%, respectively. The groups were similar in age, marital status, body mass index, use of epidural, frequency of inductions, episiotomies, and shoulder dystocias. The OA group had a higher frequency of rotational forceps (16.2% vs 5.9%, P = .03), greater birth weights (3304 +/- 526 g vs 3092 +/- 777 g, P = .004), and a larger percentage of white women (48.8% vs 34.3%, P = .04). Overall, 35% of forceps deliveries resulted in a third- or fourth-degree laceration. Anal sphincter injury occurred significantly more often in the OP group compared with the OA group (51.5% vs 32.9%, P = .003), giving an odds ratio of 2.2 (CI: 1.3-3.6). In a logistic regression model that controlled for occiput posterior position, maternal body mass index, race, length of second stage, episiotomy, birth weight, and rotational forceps, OP head position was 3.1 (CI: 1.6-6.2) times more likely to be associated with anal sphincter injury than OA head position. CONCLUSION: Forceps-assisted vaginal deliveries have been associated with a greater risk for anal sphincter injury. Within this population of forceps deliveries, an OP position further increases the risk of third- or fourth-degree lacerations when compared with an OA position.     

分娩方式对产后妇女粪失禁及尿失禁的影响

目的 调查女性产后粪失禁和尿失禁的发生率及其相关因素.方法 电话随访2006年10月1日至2007年9月30日在北京大学第一医院妇产科分娩的产妇,共纳入2012例妇女,收集其产后6个月内粪失禁和尿失禁的症状.采用Logistic回归法分析分娩方式与尿失禁和粪失禁的关系.结果 (1)参与调查的2012例产后妇女,14例(0.70％)有粪失禁症状.Logistic回归分析显示,粪失禁与阴道产钳助产(OR=20.09,95％ CI:3.64～110.90,P=0.000)和会阴侧切术分娩相关(OR=6.11,95％ CI:1.29～28.80,P=0.024).(2)2012例妇女中产后尿失禁、压力性尿失禁(stress urinary incontinence,SUI)、急迫性尿失禁(urge urinary incontinence,UUI)、混合性尿失禁(mixed urinary incontinence,MUI)的发病率分别为10.04％(202例)、8.15％ (164例)、0.94％(19例)和0.94％(19例).Logistic回归分析显示,与SUI相关的因素有:母亲年龄(OR=1.07,95％ CI:1.04～1.11,P=0.000)、母亲分娩前体重(OR=1.04,95％CI:1.02～1.06,P=0.001)、新生儿头围(OR=1.20,95％ CI:1.05～1.39,P=0.010)、会阴侧切术分娩(OR=4.96,95％ CI:3.05～8.07,P=0.0005)、阴道自然分娩(OR=5.22,95％ CI:2.53～10.76,P=0.000)和阴道产钳助产(OR=9.20,95％ CI:4.07～20.79,P=0.000).与UUI相关的因素有:产妇分娩前体重(OR=1.51,95％CI:1.12～2.05,P=0.008).与MUI相关的因素有:产妇分娩前体重(OR=1.06,95％ CI:1.00～1.11,P=0.049)、第二产程时限(OR=1.01,95％ CI:1.00～1.03,P=0.010)、会阴侧切术分娩(OR=7.76,95％ CI:1.42～42.52,P=0.017)和阴道产钳助产(OR=15.21,95％ CI:1.61～143.44,P=0.018).(3)产后4d和产后42 d SUI的发病率较高分别为7.95％和9.10％.结论 (1)本院产后妇女粪失禁和尿失禁的发病率较先前报道的其他地区的发病率低.(2)阴道分娩是妇女产后粪失禁和尿失禁发生的高危因素,特别是阴道产钳助产和会阴侧切术分娩.(3)母亲的年龄、分娩前体重、新生儿出生时头围、阴道自然分娩、产钳助产、会阴侧切术是发生尿失禁的高危因素.     

Risk factors for anal sphincter tear in multiparas

OBJECTIVE: To assess maternal, newborn, and obstetric risk factors associated with anal sphincter tear in multiparous women. METHODS: This case-control study identified 18,779 multiparous vaginal deliveries from 1992 to 2004 from an obstetric automated record database at the University of Alabama at Birmingham. Two hundred eighty-four patients were selected, 145 cases and 139 controls. Variables from the index pregnancy and prior pregnancies were analyzed, and multivariable logistic regression models were constructed to determine significant predictor variables for anal sphincter tear in multiparous women. RESULTS: One hundred forty-five multiparous women with no history of cesarean delivery sustained a sphincter tear. Multivariable logistic regression showed a significant association with episiotomy (odds ratio [OR] 16.3, 95% confidence interval [CI] 7.7-34.4), shoulder dystocia (OR 7.9, CI 1.6-38), forceps delivery (OR 4.7, CI 2.0-11.2), and being married (OR 2.2, CI 1.1-4.6). A second exploratory model that included variables from previous pregnancies, showed that in addition to episiotomy (OR 34.6, CI 8.8-136), shoulder dystocia (OR 11.1, CI 1.3-95.2), forceps delivery (OR 6.1, CI 1.6-23.5), previous sphincter tear (OR 7.7, CI 1.2-48.7), and second stage of labor greater than 1 hour (OR 6.7, CI 1.1-42.5) were associated with tear. CONCLUSION: The strongest clinical risk factors for anal sphincter tear in multiparous women are episiotomy, shoulder dystocia, previous sphincter tear, prolonged second stage of labor, and forceps delivery. LEVEL OF EVIDENCE: II-2.     

Episiotomy and perineal lesions in spontaneous vaginal deliveries.

OBJECTIVE: To evaluate the influence of mediolateral episiotomy on the perineal state after spontaneous, singleton vaginal deliveries with fetus in the occiput anterior position. DESIGN: The study was a population based, observational study. Two approaches were used in the analyses. Initially, we considered the parturients as quasi-randomised to one of three equally sized groups of midwives with different attitudes towards episiotomy. Secondly, we studied the effect of episiotomy on the state of the anal sphincter, controlling for birthweight, parity, and duration of second stage of labour. SUBJECTS: 2188 pregnant women delivering consecutively. MAIN OUTCOME MEASURES: Perineal lacerations and tear of the anal sphincter. RESULTS: Women allocated to the group of midwives with the lowest rate of episiotomy were more likely to have intact perineum after delivery (OR = 1.8 (1.4-2.2)), had a slight tendency towards more perineal lacerations (OR = 1.3 (1.0-1.5)), but no increase risk of having tear of the anal sphincter, compared with the women allocated to the two groups of midwives with higher frequencies of episiotomy. The second approach showed that episiotomy was related to an increased risk of tear of the anal sphincter (OR = 2.3 (1.2-4.6)). However, this relation was not found among the group of parturients delivered by the midwives with the lowest rate of episiotomy (22%). CONCLUSIONS: Our results encourage a conservative approach to the use of mediolateral episiotomy, and in the light of previous findings, it seems reasonable to suggest that episiotomy should ideally be used in about one in five spontaneous vaginal deliveries.     

Third degree obstetric perineal tears: risk factors and the preventive role of mediolateral episiotomy

Objective To determine risk factors for third degree obstetric perineal tears and to give recommendations for prevention.
Design Retrospective case–control study.
Setting A teaching hospital in The Netherlands.
Participants and methods One hundred and twenty cases of vaginal delivery complicated by third degree perineal tear and 702 uncomplicated vaginal deliveries were compared, with respect to possible risk factors.
Results In a multivariate model high birthweight, forceps delivery, induced labour, epidural anaesthesia and parity were risk factors for anal sphincter tear. In addition, mediolateral episiotomy was associated with fewer sphincter injuries. Separate analysis of nulli- and multiparous women demonstrated that high birthweight and epidural anaesthesia (increased risk) and mediolateral episiotomy (decreased risk) were factors associated with anal sphincter tear only in nulliparous women.
Conclusions We found several risk factors for anal sphincter tear. Nulliparous women are at higher risk than multiparous women. Mediolateral episiotomy may be sphincter-saving especially in nulliparous women and therefore prevent them from chronic faecal incontinence.